Provides ustekinumab drug concentration and anti-ustekinumab antibodies in order to optimize treatment and facilitate clinical decision-making.

This assay may be helpful in any patients on ustekinumab therapy for Crohn's disease, psoriasis, or other autoimmune conditions.

Gold serum separator (SST) tube

Immediately following collection, mix sample thoroughly by gentle inversion, 5 times

1. Allow sample to clot for a minimum of 30 minutes
2. Spin within two (2) hours of sample collection

Gold serum separator (SST) tube

Red serum vial/tube - 5 mL

Lavender (EDTA), 4mL

Dk green heparin (Li or Na), no gel

Lavender/Dk green:

Immediately following collection, mix sample thoroughly by gently inverting 8 - 10 times, to prevent clotting

Red:

1. Allow a minimum clotting time of 30 to 60 minutes for the serum tube
2. Spin
3. Transfer serum to a Transfer vial/tube with cap - 12mL (LabCorp), labelled as serum, within two (2) hours of sample collection

Lavender/Dk green:

1. Spin
2. Transfer plasma to a Transfer vial/tube with cap - 12mL (LabCorp), labelled as the appropriate plasma type, within two (2) hours of sample collection

Ambient (preferred) - 14 days

Refrigerated - 14 days

Frozen - 14 days

Freeze/thaw cycles: Stable x 6

Electrochemiluminescence immunoassay (ECLIA)

Ustekinumab: <0.1 μg/mL

• Result ≥0.1 μg/mL indicates detection of ustekinumab
• In the presence of anti-ustekinumab antibodies, the ustekinumab drug level reflects the free, antibody-unbound fraction of ustekinumab in serum.

Anti-ustekinumab antibody: <40 ng/mL

• Result ≥40ng/mL indicates detection of anti-ustekinumab antibodies.

Drug assay:

The ustekinumab drug level typically reflects the antibody-unbound (the free fraction) of ustekinumab when serum anti-ustekinumab antibodies are present. In the absence of anti-ustekinumab antibodies, the ustekinumab drug level typically reflects the total ustekinumab concentration in serum.

Anti-drug antibody assay:

This anti-ustekinumab antibody assay is “drug-tolerant,” that is, the presence of serum ustekinumab does not impede the detection and quantitation of anti-ustekinumab antibodies. This anti-ustekinumab antibody assay is specific; antibodies against other biologic drugs do not cross-react with this assay. All positive anti-ustekinumab antibody results are verified by a confirmatory test.